Certain vehicular or industrial applications use engines that require a fuel additive. In particular, a diesel fuel engine may require an additive, such as cerium, to be added to the fuel prior to the combustion process. Due to increased concerns about emissions from internal combustion engines, as well as other sources, it has become a design constraint to reduce the overall level of emissions created. As a result, in the example of a diesel engine, the amount of cerium added to the fuel must be precisely controlled to optimize particulate control and minimize the environmental impact.
Previous approaches for mixing an additive with a fuel in a system suffer from problems in providing an accurate dose of additive. If the proper dose of additive is not realized, additional problems are created in that the amount of emissions may be increased to an unacceptable level. Additionally, an unused amount of additive must be recovered from the system after the useful life of the device has expired. If the dose of fuel additive is not accurately controlled, the additive tank must be increased to a larger size to accommodate larger amounts of additive that may not be required in the useful life of the system. As a result, it would be desirable to provide a system for mixing a fuel additive with a fuel that provides a precise amount of additive in response to refueling conditions.
U.S. Pat. No. 4,621,593 discloses an apparatus for adding a fluid agent to the fuel supply of an automotive engine. The reference generally requires the use of an additional fuel system level sender, requires a switch at the fuel cap for refueling recognition, suffers from difficulties in false level measurements due to non-level vehicle attitude, suffers from improper dosing during a power down situation during refueling and requires solenoid power during a condition when the vehicle is powered off. Additionally, the apparatus dispenses the additive in the main delivery line which may result in inadequate mixing, uses analog circuitry which may provide inaccurate dosing values and uses vulnerable high current control within the fuel tank for excitation of the pump which may create potentially hazardous conditions.
An alternate previous approach may be found in the publication entitled EOLYS.TM., published by Rhone-Poulenc on Feb. 19, 1995. Such approaches consist of either premix of additive in the fuel by the fuel supplier or local mixing at the refueling station. Neither is acceptable for the foreseeable future since vehicles not equipped with the particular trap would pass thru the oxides of cerium which are detrimental to the environment.